Process for converting a cyclic acetal to a polyolefin



' Patented June 6, 1944 UNITED STATES PATENT OFFICE PROCESS FOR CONVERTING A CYCLIC AGETAL TO A POLYOLEFIN Louis A; Mikeska, Wcstfleld, and Erving Arondale, Colonia. N. J., assiznors, by mesne assignments, to Jasco, Incorporated, a corporation of Louisiana N Drawing. Application December-7, 1940, Serial No. 369,134

12 Claims. (Cl. 260 -681) The present invention involves a method for the dehydrahydrolysis of cyclic acetalsto polyolefinic compounds. The dehydrahydroly'sis of cyclic acetals is accomplished by refluxing the cyclic acetal with a dilute acid-acting compound under fractionation conditions, the polyolefin being distilled off as it is formed. The dehydrahydrolysis'process consists in the simultaneous the present invention are hydrolysis of the cyclic acetal to a polyhydrlc alcohol and the dehydration of said alcohol to a polyolefln. I k

Dioleflns have previously been prepared by such methods as the dehydration of the corresponding glycol or unsaturated alcohol, the dehydrochlorination of-the corresponding dichloride or unsaturated chloride andthe dehydroq genatlon of mono-olefinic or paraflinic hydrocarbons.

example, dimethylbutadiene has heretofore been formation of pinacol from acetone and the dehydration of the former to the diolefin.

According to the present invention, conjugated polyoleflnic compounds, of which the conjugated dioleflns are representative, are prepared'from Other methods have also been used, but they are rather involvedand uneconomical. For

hydrocarbon-substituted meta-dioxanes or diox- V The meta-dioxanes are cyclic acetals havinglthe olanes. possessing six-membered rings and following general formula:

v wherein X is a secondary or tertiary carbon atom,

and R1, R2, R3, R4, Ra, R6, R1, and Rs are hydrogen or halogen atoms, alkyl, alkenyl, aryl, aralkenyl, alicyclic,=aralkyl, or alkaryl radicals, or substituted derivatives thereof, such as haloalkyl, alkoxy, aryloxy, carbalkoxy, hydroxyalkyl radicals, of which at least one of the radicals R1 and R2 must be an alkyl, alkenyl, aralkyl, halo alkyl or alkoxy alkyl radical, and the like.

When a meta-dioxane has a substituent containing a double bond between a pair of carbon atoms, the product derived from said meta-dioxane by dehydrahydrolysis is a triolefln. Compounds containing two meta-dioxane rings tree I from unsaturated substituents yield tetraoleflns upon dehydrahydrolysis; Hydrocarbon-substi- 20 prepared by a lengthy procedure involving the tuted dioxolanes (cyclic acetals containing a fivemembered ring) can also be dehydrahydrolyzed I I H i-meth iniemgumiieji V Jon. cm,

v 0 E0011; omocm' cmcom' 2,2,4,4',5,6,e-h m methyl meta-dioxana a cm om I O CH|-- v cnicn'n cm,

0 Y 2,4,4,6-tetra methyl mesa-dim CH: CH:

0 cHr- OH: H H: 0

2,4,4-trimethyl meta-diorama cm H C 0 900E: (1H, if;

4,5-dlniethyl meta-diorama ot v.

c-alca-cnca-oa. bullion-u H: cmcn-c-on-oncn.

I-metbvlbmdimi-f,

OBI clmcn-o-cn-cm t-mothylheudienc-ht OH. OBI OKs-l -OB CHI 8,4-dimethylpentadisns-IJ CH: CH. CH:

cm- -o QJJ-tflmethylpmdatidnl-LI can.

. CBF -CH:

I-mcthyM-chlorobutadleno-LI CHsOHcOOlKe can: 4:11-03 tethesycthylbutadionc-i, l

CHs Cane CBpi5 -JJ=OB0 S-mctbyl-I-othylbutadlene-i, 0

0K0 CHI cnpc-cn c-cm 3,4-dimcthylpentadieno-L8 CH0 CHI 'CHF-CH= OH H 2,6-dlmethylhendiene-L8 011: C(GHI)| J; =CH| a-methyH-t-hntylbntadisne-l, 1

The reaction of the present invention is one or dehydrahydrolysis in which cyclic acetals are This reaction may be illustrated as follows:

The catalysts which are effective in promoting the reactions involved in this invention are acidic in character, and may be classified into two general groups. mineral and organic. In the mineral classification are mineral acids. mineral acidacting compounds (e. 3., mineral acid-acting salts) and other substances which are capable of acting as mineral acids in the presence of water or under the conditions of the reaction. Mineral acid catalysts include HCl, H2804, HNOa, HIBr.

4, 825201. HPOs, H4Pa01, HF, ClSOsH, FSOsH, silicotungstlc acid, boron fluoride-water complexes, fluosilicic acid, and the like. The following mineral acid-acting salt catalysts may be mentioned: EeCla, ZnCla, ZnSOr, AlCla, FaflSOOs, Nell-I804, AMSOO NaI-IzPO4. etc. Illustrative of the compounds which form acids with water and which may be used in the presence of water as catalysts for these reactions are SOzClz,

- present invention. These include aliphatic carboxylic acids, such as formic and oxalic acids, halogenated organic acids, such as chloroacetic acid, aliphatic and aromatic sulfonic acids, such as hexyl and phenyl sulfonic acids, alkyl and dialkyl sulfates, such as monoand diethyl sulfates, allwl phosphoric acids, acid halides, sulfoacetic acid, aniline hydrochloride and hydrobromide, and the like. The cyclic acetals can also be dehydrahydrolyzed by treating a water solution thereof with a tertiary alkyl halide or another compound which decomposes to produce converted into the corresponding polyoleiinic an acid under the reaction conditions.

Mixtures of the above catalysts may also be employed; for example, inorganic salts such as zinc chloride, calcium chloride, zinc sulfate, ammonlum' chloride, etc. may be added to mineral acids as reaction promoters. Such salts increase the activity of the catalyst. A mutual solvent such as ethylene glycol may be used to provide better contact between the cyclic acetal and the aqueous acid-acting catalyst. Organic acids having a relatively low hydrogen ion concentration. such as acetic acid, can be promoted ac catalysts for these reactions b adding small amounts of,

sulfuric acid. other mineral acids, or mineral acid saltstothem.

The acid concentration of the catalyst should not exceed 50%, and may range between 0.05 and 50%. With the mineral acid catalysts, the best results are obtained with acid concentrations ranging from 1 to 5%. A decrease in the acid concentration tends to improve the diolefin yield, but results in an increased reaction time. A decrease in the volumeof the aqueous catalyst per unit weight of cyclic acetal also results in an increased reaction time but, in most instances, does not aii'ect the diolefln yield. Thus, the use of large volumes of aqueous catalyst is beneficial, since increased reaction speeds result therefrom,

Very dilute acid catalysts (cos-1.0% concentration) can be used together with an inorganic salt as a promoter. More concentrated acid catalysts (-50% concentration) may be used at lower reaction temperates; in such cases, the

reaction may be carried out under a partial vacuum. The strong organic acids. such as chloroacetic acid, can be used either undiluted or in solution in water or a solvent such as chloroform or ethylene dichloride. In any event, a catalyst vated temperatures and pressures are required for the conversion of cyclic acetals in which K (see formula, page 1) is a secondary carbon atom. It has also been found that the time required for the completion of the reaction likewise depends upon the type of cyclic acetal used and the conditions of temperature and acid 001106!!! tration. The time range within which the reac tion is completed extends from 0.1 to 16 hours. With cyclic acetals in which X is a'tertiary carbon atom, the conditions of temperature and acid concentration may be varied to bring the reaction time within the limits of from 0.1 to 8 hours. Cyclic acetals in which X is a secondary carbon atom require from 4 to 12 hours depending upon conditions of temperature and acid concentration. Dehydrahydrolysis of cyclic acetals may also be carried out at elevated temperatures and pressures in the absence of a catalyst or in the presence of a very dilute catalyst.

The process of the present invention may be carried out in either a batch or continuous fashion and in either the liquid or vapor phase; The process may be carried out in a continuous manner in one of several ways: i

(1) The cyclic acetal may be added slowly to a heated reaction vessel containing the catalyst, the reaction mixture being agitated to provide good contact between the cyclic acetal and catalyst, and the polyolefln being fractionated oil as formed. The condensate is then dried over potassium carbonate or. other dessicating salt and refractionated. An aldehyde is a b'y-product of the reaction. If desired, sulfur dioxide, sodium bisulfite, a tertiary alcohol, a tertiary olefin, ora tertiary halide may be charged to the reactor simultaneously with the cyclic acetal to unite with the liberated aldehyde and thus prevent the olymerization of the aldehyde or side reactions between the aldehyde and the diolefln before the removal of the latter from the reaction system.

The aldehyde may also be distilled from the reactor along with the poly-olefin.

(2) The cyclic acetal and dilute acid-acting catalyst may be passed through a heated, packed I of such a nature and concentration that it will I reactor either in concurrent or countercurrent direction, the resulting diolefln bein g' separated from the reaction mixture by fractionation, and any unreacted materials being recycled to the reactor.

(3) The cyclic acetal may be passed together with steam over an acid catalyst deposited on a carrier or over solid acid-acting salt at elevated temperatures. The poly-oleflnic products of these reactions may be purified by refractionation. The dehydrahydrolvsis of cyclic acetals formed from formaldehyde yields reaction distillates containing almost pure p ly-oleilns. Distillates obtained during the dehydrahydrolysis of cyclic acetals formed from higher molecular weight aldehydes than formaldehyde usually contain both the aldehyde and the poly-olefin. I The aldehyde and polyolefln may be separated from each other by fractionation of the distillates containing them; the aldehyde may be recycled by converting it into a cyclic acetal which can then be treated according to the process of this invention. Byproducts formed in these reactions may be recycled, if desired, or may be used as such in further synthesis, as solvents, or as blending agents for gasoline, etc.

Cyclic acetals suitable as starting materials for this process may be prepared by the condensation of olefins (see copending application Serial No. 334,668; filed May 11, 1940), other unsaturated compounds, or secondary or tertiary alcohols with aldehydes in the presence of dilute mineral acids. When it is desired to produce poly-oleflns from meta-dioxanes obtained according to the method disclosed in copending application Serial No. 334,668 referred to above, it is not necessary to isolatethe meta-dioxanes; instead, the olefinaldehyde reaction mixtures containing them may be diluted with water to the desired acid concentration, and the diluted mixtures may then be refluxed under fractionation conditions, the polyoleflnic products being taken off overhead as formed. Cyclic acetals may'also be prepared by condensing glycols or other polyhydric alcohols with aldehydes.

The importance of this invention may be realized when it is pointed out that only meager poly-olefin yields are obtained when cyclic acetals are heated with a dilute acid catalyst under such conditions that none of the reaction products are removed from the reaction zone until completion of the reaction. Only when the poly-olefin is removed continuously (by distillation) as it is formed are satisfactory poly-olefin yields attained. The refluxing feature of this invention insures contact of the cyclic acetal with the acidic catalyst at a readily controlled temperature for a period sufficient for the complete conversion of the cyclic acetal. Thus, whether the process of this invention be applied to cyclic acetals per se or to olefin-aldehyde reaction mixtures containing cyclic acetals, this invention represents a distinct and advantageous advance over period art methods for producing polyolefins.

The conjugated poly-oleflns made in accordance with this invention are useful in the preparation of synthetic rubbers, as intermediates in other chemical reactions, and as blending agents for gasoline. butadiene has an octane blending value of 212.

The following examples are given for the purpose of illustrating the invention:

Example 1 260 parts by weight of i,-i,5-trimethyl metadioxane (boiling point: 152C), and v1240 parts by weight of 5% sulfuric acid were placed in a reactor equipped with a stirrer and a fractionating tower. The mixture was stirred and heated to For example, 2,3-dimethylv a temperature of between 95' and 100 C., at which temperature the reaction started. The i'racticnating tower temperature was maintained between 60 and 63 C. until all 01' the diolefln formed in the reaction was removed hours);

the complete removal of the diolefin was indicated by a sudden rise in the fractionating tower temperature. The distillate from the iractionator was composed oi- 74.4 parts by weight of 2,8-dimethylbutadine-1,3 and 68 parts by weight of water.- The 2,3-dimethylbutadiene-1,3 was purified by reiractionation. The pure dioleiin boiled at 88.5 C. (756 mm.) the product of its reaction with maieic anhydride melted at '78'-'l8.5' C.

I Example 2 v 260 parts by weight of 4,4,5-trimethyl metadioxane and 1215 parts by weight oi 2.5% HCl were charged into a reactor equipped as in Example l. The mixture was then heated at 94- 97 C. under fractionation conditions for 4 hours as in Example 1. The distillate was purified, yielding '19 parts by weight or 2,3-dimethyl- Example 3 'butadiene-L3.

Example 4 260 parts by weight of 4,4,5-trimethy1 metadioxane and 1220 parts by weight of 2.5% hydro bromic acid were heated for 8 hours at 95-9'1 C. in accordance with the method described in Example 1. The purified distillate was composed of 77.0 parts by weight of 2,3-dimethylbutadiene-L3.

Example 5 260 parts by weight of 4,4,5-trimethyl metaacid were heated for 'l'hours at95-97" C. in accordance with the method described in Example 1, yielding 69 parts by weight 01' 2,3-dimethylbutadiene-1,3. Example 6 100 parts by weight of 4,4,5-trimethyl metadioxane and 157 parts by weight of dichloroacetic acid were heated for minutes at the" refluxing temperature of the mixture in accordance with the method described in Example 1, yielding 15 parts by weight of 2,3-dimethylbutadiene-l,3.

Example 7 260 parts by weight of 4,4,5-trimethyl meta- I dioxane and 1200 parts by weight oi a 0.2% RC1 solution containing 360 parts by weight of calcium chloride yielded 85 parts by weight of 2,3-dimethylbutadiene-L8 on being heated for 5 hours at 99-,-101,C. in accordance with the method described in Example 1.

Eaxzmple 8 260 parts by (weight of 4,4,5-trimethyl metadioxane' and. 1400 parts by weight of 2.5% H01 dioxane and 1215 parts by weight of 2.5% nitric in ethylene glycol were heated for one hour at a temperatureof 96 to 100 C. in accordance with the method described in Example 1, the

4 time 9 parts by weight oi paraiormaidehyde, 118

parts by weight of 25% sulfuric acid. and 246 parts by weight of trimethylethylene were placed in a closed container, and the whole was shaken for 5-6 hours. The formaldehyde reacted completely. The reaction product was diluted with 475 parts of water, and the diluted mixture was stirred and heated under fractionation conditions at a temperature of 95"-99 C. for 7 hours. The distillate was taken overhead at 64C. until the reaction terminated and then the fractionation was continued until the head temperature reached 83 C. The distillate was dried over K260: and fractionated, 94 parts by weight of trimethylethylene boiling at 26-41 C., 2.3 parts by weight of a mixture of trimethylethylene and 2,3-dimethyibutadiene-l,3 boiling at 41-65 C., and 54 parts by weight of 2,3-dimethylbutadiene-1,3 boiling at 65-'l3 C. being obtained thereby.

Example 10 Example 11 196 parts by weight of 2,4,4,6-tetramethyl metadioxane (boiling point: l38-140 C.) and 960 parts by weight of 2.5% HCl were heated for 2.5 v

hours in accordance with the method described in Example 1, the reactor temperature being 90-96 .C. and the fractionating tower temperature being 56-63 C. Purification oi the distillate yielded 37 parts by weight of 2-methylpentadiene-1,3 (boiling point: 75 C.; melting point of its maleic anhydride addition product: 58-58 .5 C.) and 25 parts by weight of acetaldehyde.

Example 12 170 parts by weight of 2,4,4,5,6-pentamethyl meta-dioxane (boiling point: -162.5 C.) and 820 parts by weight oi 2.5% H01 were heated for 2.25 hours at 89-95 C. in accordance with the method described in Example 1, the iractionating tower temperature being 63-70 C. Upon purification of the distillate, 35 parts by weight of 2,3- dimethylpentadiene-1,3 (boiling point: 105-106 C. at 756 mm.: melting point 01 its maleic anhydride addition product: 80-.80.5 C.) were obtained.

We claim:

l. A process for the production of 2,3-dimethylbutadiene-Lii which comprises refluxing 4,4,5-trimethyl meta-dioxane for from 0.1 to 8 hours with 1-5% sulfuric acid and removing the 2,3-dimethylebutadiene-lfi as formed.

2. A process for the production of isoprene which comprises refluxing 4,4-dimethyl meta-dioxane for from 0.1 to 8 hours with 1-5% sulfuric acid and removing the isoprene as formed.

3. A process for the production of 2-methylpentadiene-1,3 which comprises refluxing 2,4,4,6- tetramethyl meta-dioxane for from 0.1 to 8 hours with 1-5% sulfuric acid and removing the 2- methyl-pentadiene-IB as formed.

4. A process for the production of 2,3-dimethy1- butadiene-1,3 which consists in reacting paraformaldehyde, 25% sulfuric acid and trimethylethylene in a closed container for six hours, diluting the reaction mixture with water to an acid 2,350,517 poly-oleflns which comprisesfrefiuxing a cyclic 1 concentration of 5% and heating the diluted mixture under reflux conditions at a temperature of 95-99 C. while taking overhead a distillate between the temperatures of 64 C. and 83 0., drying and fractionating the distillate to recover the 2,3-dimethylbutadiene-1B'.

5. A process for theproduction of 2,3-dimethylbutadiene-1,3 which consists in reacting 120 parts by weight of para-formaldehyde, 118 parts by weight of 25% sulfuric acid and 246 partsby weight of trimethylethylene in a closed container for 6 hours, dilutingthe reaction mixtur with 4'75 parts of water and heating the diluted mixture under reflux conditions at a temperature of 95-99 C. for 7 hours while taking overhead a distillate between the temperatures of 64 C. and 83 C., drying andfractionating the distillate to recover-the 2,3 dimethylbutadiene-LB.

6; A process for the production of conjugated polyolefln which comprises refluxing a cyclic acetal possessing the formulaacetal possessing the formula- V w stituentselected from the group consisting of alkyl, alkenyl, aryl, aralkenyl, alicyclic, aralkyl, al-

karyl, halo-alkyl, alkoxy, aryloxy, carbalkoxy and hydroxy alkyl radicalaand R1,.Rz, R4, R5, R0, R1.

and Rs are substituents selected from the group consisting of hydrogen and halogen atoms, alkyl,

alkenyl, aryl, aralkenyl, alicyclic, aralkyl, alkaryl,

rhalo-alkyl, alkoxy, aryloxy, carbalkoxy and hydroxy alkyl radicals for from 0.1 to 8 hours with an aqueous acid reacting material having an acid I concentration 01' 0.05-50% at a temperature between 90 and 150 C. under a'pressure ranging from a partial vacuum to several atmospheres and removing the poly-olefins as formed.

9. The process as defined in claim '7 in which 2 the cyclic acetal is refluxed for from 0.1 to 12 hours and the aqueous acid-reacting material is dilute aqueous hydrochloric acid having an acid concentration of 15%.

10.-'A process for the production of a conjugated r diene which comprises refluxing a cyclic acetal,

' possessing the formula- I.

wherein X is a carbon atom selected from the I group consisting of secondary and tertiary carbon atoms; R1, R2, R3, R4, R5, Ra, R1 and Rs are substituents selected from the group consisting ot.hydrogen and halogen atoms, alkyl,

alkenyl, aryl, aralkenyl, allcyclic, aralkyl, alkaryl, halo-alkyl, alkoxy, aryloxy, carbalkoxy an hydroxy alkyl radicals for from 0.1 to 16 hours with an aqueous acid-reacting material having an acid concentration of 0.05-50%, at a temperature between 50 and 150 C. and removing the polyolefln as formed. 5

'1. A process for the production of conjugated polyolefln which comprises refluxing a cyclic acetal possessing the formula-,-

8. A process for the production of conjugated wherein X is a carbon atom selected from the v group consisting of secondary and tertiary carbon atoms; R1, R2, R3, R4, R5, Re, R: and Rs are substituents selected from the group consisting of hydrogen and halogen atoms, alkyl, alkenyl, ary l,.

aralkenyl, alicyclic, aralkyl,.all aryl, halo-alkyl, alkoxy, aryloxy, carbalkoxy and hydroxy alkyl radicals for from 0.1 to 12 hours with an aqueous acid-reacting material having an acid concentration of 1-5% and a catalyst promoter selected a from the group consisting of inorganic chlorides, sulfates and phosphates, at atemperaturebetween 50 and C., under a pressure ranging from partial vacuum to several atmospheres, and

removing the diene as formed.

11. A process for the production of conjugated diene which comprises refluxing a cyclic acetal possessing the formula- R: Ill-$11 RI wherein X is a carbon atom selected from the,

group consisting of secondary and tertiary carbon atoms; R1, R2, R3, R4, Ra, Ra, R1 and Rs are substituents selected from the group consisting of hydrogen and halogen atoms, alkyl, alkenyl,

aryl, aralkenyl, alicyclic, aralkyl, alkaryL'halo alkyLalkoxy, aryloxy, carbalkoxy and hydroxy alkyl radicals for from 0.1 to 12 hours withan aqueous acid-reacting material having an acid concentration of 1-5% and a mutual solvent at a temperature between 50 and 150 C. under a pressure ranging from partial vacuum to several atmospheres and removing the diene as formed. 

